The chief executives of Action for Children, the Children’s Society and the YMCA are among the many charities to have put their name to the letter, which calls for a change in funding.

The letter warns that 90 children are being taken into care every day – a record number – and more than three million children risk going hungry during the school holidays. Only three in a hundred families with disabled children believe the healthcare provided for them is adequate.

The letter calls on the government to end the cuts in funding forced on children’s services by austerity, and to take “urgent action” to put children at the heart of the government’s spending plans.

Kathy Evans, chief executive of Children England, said: “We can’t stand by and watch children pay the bill for the recklessness and debts of bankers and politicians. Austerity is not over for children, it’s getting worse - and Theresa May must stop it.”

Anna Feuchtwang, chief executive of the National Children’s Bureau and chair of End Child Poverty, said: “We’ve seen successive budgets come and go with token spending commitments for children and families. If austerity is really coming to an end, it’s high time the government puts its money where its mouth is, and makes a concrete financial commitment to the welfare of children.

“Things we once took for granted, like family support, children’s centres, and respite care for families with disabled children are now the privilege of the few. In some areas of the country, over half the children are growing up in poverty.

“For these children and the many others who need urgent help, the services, benefits and support that could provide a lifeline have been cut to the bone. We are failing our children if we don’t put them at the heart of government spending.”